Combustion chamber construction for internal combustion engines



May 26, 1936. 2,041,940 COMBUSTION CHAMBER CONSTRUCTION FOR-INTERNALcomsusnou ENGINES F. LUKER Filed Feb. 19, 1934 ATTORNEYS Patented May26,- 1936 PATENT-OFFICE COMBUSTION CHAMBER CONSTRUCTION FOR INTERNALcomnns'rron ENGINES Fred Luker, Detroit, Mich.

Application February 19, 1934, Serial No. 712,058

Claims.

This invention relates generally to internal combustion engines andrefers more particularly to improvements in the combustion chambers ofor fuels free from the so-called anti-knock ingredients, are employed inoperating the latter, since the rate of burning of such fuels in acombustion chamber increases as the compression ratio increases.Increasing the rate of flame travel effects an increase in the rate ofpressure rise per degree of crank travel with the result that peakpressure will be reached in the' chamber when the crank is closer to itstop dead center position and accordingly any increase in pressureresulting from raising the "compression ratio, instead of actuallyraising the power output of the engine may. be entirely sacrificed insupplying the addi-' tional torque required to compensate for loss inleverage resulting from applying maximum pressure to the crank when thelatter is at a point relatively'close to its top dead center position.Thus it must be admitted that combustioncontrol is a definiterestriction to the extent to which the compression ratio may be raised,and any attempt to increase this ratio above the limit established bythe foregoing factors merely results in practically no gain in poweroutput and excessive roughness in engine performance.

The present invention contemplates a chamber of such design as to permitaccurately controlling the rate of pressure rise per degree of cranktravel irrespective of the compression ratio, and

' thereby renders it possible to employ ratios considerably higher thanheretofore thought commercially practical, without sacrificing thecombustion control necessary in order that the increase in pressuresresulting from higher compression ratios will be reflected in the poweroutput of the engine free from combustion harshness or roughness insteadof being lost in overcoming the less advantageous crank angle usuallysynonymous with higher compression ratios.

In accordance with this invention, the rate of pressure rise per degreeof crank travel is deflnitely controlled by the provision of means inthe chamber for efiecting a lag in the rate of buming of the fuel sothat the interval of time between ignition and peak pressure is delayedto such an extent as to permit the crank to assume an advantageousposition past the top dead center position before maximum pressure isapplied to the 1 same.

More specifically, the present invention con-' templates dividing thechamber into two parts; or, in other words, consists in separating thelast portion of the charge to burn from the first portion of the chargeto burn and establishing communication between said portions through themedium of an opening or port restricted to such an extent as toretard'free transmission of the pressure built up by the burning chargein the first portion of the chamber to the second part of the chambercontaining the last fuel mixture to burn. The result is that thepressure built up by the burning charge in the first part of the chamberis prevented from materially influencing the rate of pressure rise ofthe last fuel mixture to burn. This construction not only provides forreducing the rate of pressure rise per degree of cranktravel, but alsominimizes the tendency of the chamber to detonate since it is wellestablished that detonation is initiated in a combustion chamber at theextreme-end of the flame travel due to the compression of some rel-vatively small portion of the unburned charge by the approaching flame.

In addition to the foregoing, this invention contemplates a combustionchamber of the type previously set forth so designed as to provide forcompletely filling the cylinders of the engine with fuel mixture and tootherwise improve the performance of same.

With the foregoing, as 'well as other objects in view, the inventionresides in the peculiar construction of the combustion chamber whichwill be made more apparent as this description proceeds, especiallywhenconsidered in connection with the accompanying drawing wherein:

Figure 1 is a fragmentary elevational view of the combustion chambersurface of a cylinder head;

Figure 2 is a cross-sectional view taken substantially on the line 2-2of Figure 1;

Figure 3 is a sectional view taken on the plane indicated by the line3-3 of Figure 1;

Figure 4 is a diagram to be more fully explained hereinafter.

Although it will be apparent as this description proceeds that thecombustion chamber embodying the inventive principles involved hereinmay be advantageously employed .in association with various types ofcylinder heads, nevertheless, I have shown thesame herein, for thepurpose of illustration, as employed in. connection with a water-cooledcylinder head of the L type. Before going into a detailed discussion ofthe combustion chamber, reference will be made to Figure 4 of thedrawing in an eiiort to illustrate diagrammatically the effect thatincreasing the rate of flame travel by raising the compression rate hason the interval peak pressure is reached in relation to the degree ofcrank travel.

In Figure 4 of the drawing, I have illustrated two pressure rise curvesof two combustion chambers in relation to the path of travel A of anengine crank. The curve designated by the character B indicates thepressure rise of a combustion chamber design considered commerciallysatisfactory by the trade and the curve C represents the pressure riseof a chamber designed in 'accordance with this invention. The points D",E, F, and Gf on the above curves respectively represent the point atwhich ignition takes place; the pressure at the top dead center positionof the crank; the point past dead center peak pressure is reached in achamber having the curve B" and the point past dead center peak pressureis reached in a chamber having the curve -C.

Projecting the aforesaid points down upon the path of travel A of thecrank reveals the fact that the point G, or the point at which peakpressure is reached on the curve C, is located at a greater angle pastdead center than the corresponding point F on the curve B, with theresult that considerably greater effort would have to be exerted at thepoint F than at the point G in order to transmit the same torque to thecrank. Consequently, even though the two aforesaid chambers havesubstantially the same compression ratio, the one having the curve C orthe one embodying the principles of this invention will transmit anappreciably greater amount of torque to the crank due to the moreadvantageous leverage at which the maximum pressure is applied.

As a matter of fact, it is entirely possible to have a condition whereina combustion chamber embodying the principles of this invention may havea lower compression ratio than the conventional chamber represented bythe curve B" and actually produce more useful work than the chamber ofhigher compression ratio, since the rate of flame travel inthe former isless than the rate of flame travel in the latter, and accordingly peakpressure in the chamber of relatively low compression ratio is effectedwhen the crank is at a greater distance past the top dead centerposition than the corresponding peak pressure of the higher compressionchamber,

"invie'w of the foregoing, the desirability of controlling combustion insuch a manner that'maximum pressure is applied to the crank at a greaterangle past the top dead center position of the latter, is apparent sinceit ofiers the possibility of increasing the torque in an amountproportionate to the rise in the compression ratio.

In the present instance, the foregoing is accomplished by a combustionchamber so constructed as to virtually divide the last portion of thecharge to be burned from the first portion of the charge in such amanner as to provide for igniting the former charge upon completion ofthe burning of the latter charge, and to prevent the burning charge fromrapidly building up the pressure of the unburned charge. Thisarrangement not only provides for obtaining the desired combustioncontrol, but inaddition, minimizes the tendency for the chamber todetonate since the last portion of the fuel mixture to burn is notinfluenced by the burning charge to such an extent as to cause theformer mixture to reach an abnormal pressure. This feature in itselfpermits obtaining higher compression ratios than heretofore thoughtcommercially possible and, when combined with the arrangement forcontrolling combustion, provides for increasing the torqueproportionately. In detail, the combustion chamber is designated in theseveral figures of the drawing by the reference character l0, andcomprises two distinct portions exemplified in Figure '2 by thereference characters H and I2. The portion ll establishes communicationbetween the valve gallery of the internal combustion engine and theadjacent cylinder of the latter, while the portion I2 is ofcomparatively less volumetric capacity, and also communicates with thecylinder of the engine. The ratio of the volume of the portion II to thevolume of the portion l2 will vary in dependence upon the compressionratio and the lag it is desired to effect in attaining maximum pressure.Consequently, it should be understood that, in the specific embodimentof the invention,

the relative volumes of the two aforesaid portions of the chamber areespecially calculated for one application only, and may be varied inaccordance with the results desired.

The two portions II and I2 of the chamber Ill are separated by apartition I3 extending transversely of the chamber over the cylinder ofthe engine and establishing communication between the two portions ofthe chamber by means of a restricted port or opening i4. Of course, thetwo aforesaid portions of the combustion chamber will also communicatewith each other around the lower end of the partition l3, but since thelatter end of the partition is arranged flush with the bottom face ofthe head, it necessarily follows that only a very restricted openingwill exist when the piston H5 in the cylinder, is at its top dead centerposition as shown in Figure 2 of the drawing. However, in certaininstances the area of this opening may prove detrimental, and in suchcases, means may be provided for sealing the space between the lower endof the partition and piston when the latter is at its top dead centerposition. Although various types of seals may be employed foraccomplishing this result, nevertheless, for the purpose ofillustration, I have shown the same as comprising a strip "5 ofrelatively soft metal, such as copper, embedded within the lower end ofthe partition in such a manner as to project a sufficient distance belowthe partition to engage the piston in the uppermost position of thelatter. The strip l6 extends for substantially the full width of thecombustion chamber, and if desired, the piston maybe slotted as at I! toreceive the projecting edge of the strip in the manner shown in Figure2.

Obviously, in cases where the fuel mixture in the combustion chamber isignited before the piston reaches top dead center position, a certainamount of pressure will be transmitted to the last that at this time thedesired seal is effected between the partition and the piston, therestricted port I! affords the only communication between the twoportions of the chamber. Because of the fact that the port I! forms theonly communication between the portions of the chamber, thecross-sectional area, or diameter, of the latter is highly critical, andis so determined asto permit transferringthe flame from the portion llto the portion l2, and to prevent free transfer of gases under pressuretherethrough. In other words, the relatively small cross-sectional areaof the port l4, together with the rapid rate of flame propagation,materially restricts the transfer of gases under pressure from the firstportion of the fuel mixture to burn in the section II of the chamber tothe last portion of the fuel mixture to burn in the section 12 of thechamber.

The fuel mixture in the portion I I of the chamher is ignited on thecompression stroke of the piston IS in the usual manner by the means ofa suitable spark plug l8, and the charge in this portion of the chamberis substantially completely burned before the flame ignites the fuelmixture in the portion I2 through the restricted port I4. As the fuelmixture in the portion II is burning,

the pressure in this portion of the chamber be' comes greater, but dueto the restricted nature of the port I4 and the short time intervalinvolved in burning, the rate at which the charge in the portion l2 ofthe chamber is compressed by the flame front is materially retarded withthe result that maximum pressure is not attained until the piston beginsits working stroke; or, in other words, until the crank assumes asubstantial distance past the top dead center position thereof. This lagin the rate of pressure rise effected by the partition is clearly shownby the interruption of the curve C at the point H. Inasmuch as thecross-sectional area of the port l4 controls, to a large extent, theinfluence of the burning charge'in the portion l l of the combustionchamber on the building up of the pressure in the portion I2, it will beapparent that varying the'cross-sectional area of the port offers thepossibility of varying the rate of pressure rise per degree of cranktravel.

It will be observed that the foregoing construction provides forobtaining higher compression ratios, and at the same time permitscontrolling the rate of pressure rise per degree of crank travel so thatsubstantially the entire force afforded by increased compressionpressures will actually be employed to increase the efficiency or workoutput of the engine. In addition, to the foregoing, it is to be notedthat the particular shape of the portion ll of the combustion chambershown in Figure l is such as to provide for uninterrupted flow of thefuel mixture from the intake valve [9 to the cylinder of the engine withthe result that the filling characteristics of the latter are greatlyincreased.

What I claim as my invention is:

1. In an internal combustion engine, a cylinder head having a combustionchamber divided into two portions by a partition and communicating witheach other through the medium of an opening through the partition of asize sufficient to permit the flame of the burning charge in one portionof the chamber to pass into the other portion to ignite the charge inthe latter but to retard compression of the charge in said second namedportion by the flame front in the first named portion of thechamber.

2. In an internal combustion engine, a cylinder head having a combustionchamber divided intg two portions of predetermined volumetric capacityby a partition and communicating with each other through the medium ofan opening through the partition of such a size as to materiallyreitardthe flow of burning fuel mixture under pressure fromone portion of thechamber to the other but to permit the flame to pass readily from oneportion of the chamber to the other.

the first to the second named chambers, and

means cooperating with the pistonin said cylinder to form a'seal betweensaid chambers.

4. In an internal combustion engine having a cylinder and having anintake port adjacent the cylinder, 9. piston reciprocally mounted insaid cylinder, 9. cylinder head formed with a combustion space havingtwo chambers both communicating with the cylinder of the engine, one

of the chambers being adapted to register with the i intake port and theother of said chambers being adapted to contain the last fuel mixture toburn, a partition separating the two aforesaid chambers and having anopening therethrough restricted to retard the rate of pressure rise perdegree of engine crank travel, and means sealing the space between theend of the partition and head of the piston when the latter is in itsuppermost position.

5. In an internal combustion engine having a cylinder bore and having anintake port adjacent the bore for supplying fuel mixture thereto, a headprovided with a combustion space establishing communication between theintake portand cylinder bore and composed of two chambers, one of thechambers being in direct communication with the intake port forreceiving the fuel mixture and the otherof the chambers being adapted tocontain the last portion of the fuel mixture to burn in the combustionspace,

an ignition device associated with the first named chamber, and apartition separating the chambers having an opening therethrough of a.size accurately predetermined to appreciably retard the rate ofcompression of the last fuel mixture to burn in the second named chamberby the flame front in the first named chamber, and to permit the flamein the first chamber to pass through the partition into the secondchamber for igniting the fuel mixture therein.

6. In an internal combustion engine having a, cylinder bore and havingan intake port adjacent the bore for supplying fuel mixture thereto, ahead provided with a combustion space establishing communication betweenthe intake port and cylinder bore and comprising two chambers, one ofsaid chambers communicating with the intake port for receiving the fuelmixture therefrom and the other of the chambers being adapted to containthe last fuel mixture to burn, an ignition device associated withthe'fir'st named chamber, and means in the combustion space separatingthe two chambers including a partition so disposed in the space that thechamber communicating with the intake port possesses a substantiallygreater volume than the other chamber and having an opening therethroughof a cross sectional area predetermined to appreciably retard the rateof compression of the last fuel mixture to burn in the second namedchamber by the flame front in the first named chamber and to permit theflame to pass readily from the first to the second chamber for ignitingthe fuel mixture in the latter.

7. In an internal combustion engine having a cylinder bore and having anintake port laterally offset from the cylinder bore, a piston mountedfor reciprocation in the bore, a cylinder head having a, combustionspace therein establishing communication between the intake port andcylinder and consisting of two chambers, one of said chambers beingarranged in direct communication with the intake port for receiving fuelmixture therefrom and having a portion overlying the cylinder boreandthe other of said chambers also communicating with the cylinder bore andbeing adapted to contain the last fuel mixture to burn, an ignitiondevice associated with the first named chamber, means in the combustionspace cooperating with the piston in the top dead center position of thelatter to separate said chambers including a partition formed with anopening therethrough having a cross sectional area predetermined toappreciably retard the rate of compression of the last fuel mixture toburn in the second named cham ber by the fiame front in the firstchamber to effect a lag in the rate of pressure rise per degree ofengine crank travel and also predetermined to permit the flame in thefirst chamber to pass readily into the second chamber for igniting thefuel mixture in the latter.

8. In an internal combustion engine, a cylinder head formed with acombustion chamber therein and having means for retarding the rate ofpressure rise per degree of crank travel including a partition dividinga portion of the last fuel mixture to burn in' the chamber from thefirst fuel mixture to burn and having an opening therethrough of a crosssectional area predetermined to retard the rate of compression of thelast fuel mixture to burn by the first fuel mixture to burn and alsopredetermined to permit the flame to pass readily through'the partitionfor igniting the last fuel mixture to burn.

9. In an internal combustion engine of the reciprocating piston typehaving a combustion chamber, means for igniting fuel mixture supplied tothe chamber, and means in the chamber operable upon ignition of the fuelmixture therein to retard the rate of pressure rise per degree of pistontravel including a partition in the chamber cooperating with the head ofthe piston in the top center position of the latter to divide theportion of the chamber adapted to contain the last fuel mixture to burnfrom the portion of the chamber adapted to contain the first fuelmixture to burn and having an opening therethrough establishingcommunication between the two aforesaid portions.

10. In an internal combustion engine having a cylinder and having intakeand exhaust ports adjacent the cylinder, means establishingcommunication between the ports and interior of the cylinder boreincluding a combustion chamber having a portion overlying the ports anda. part of the cylinder bore in direct communication with the latter andhaving another portion overlying the cylinder bore beyond the portionaforesaid also in direct communication with the bare, and meansseparating the portions aforesaid of the chamber including a partitionextending transversely to the direction of flow of the 'fuel mixturefrom the intake port to the cylinder and having an opening therethroughrestricted to retard the rate -of pressure rise per degree of enginecrank travel on ignition of the charge in one of the portions aforesaidof the

